Auto merge of #116018 - DianQK:simd-wide-sum-test, r=scottmcm

Increasing the SIMD size improves the vectorization possibilities

Change the `simd-wide-sum.rs` to pass tests based on the LLVM main branch.

For smaller lengths, we cannot expect to always get vectorized.

A related discussion at https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/LLVM.20HEAD.3A.20codegen.2Fsimd.2Fsimd-wide-sum.2Ers.20newly.20failing.

r? scottmcm

Author: bors